Distributed Control and Redundancy for Input-Series-Output-Series LCL-Type Grid-Connected Inverter System

Input-series-output-series (ISOS) inverter combined system is generally used in the occasion of high input and high output voltage. If the combined system topology is employed in the grid-connected application, multiple small-capacity standardized inverter modules could constitute a bulky-capacity grid-connected inverter system, which will effectively improve system reliability and facilitate system design. Nevertheless, for the sake of enhancing the system reliability authentically, distributed control and redundancy are urgently needed for the grid-tied ISOS inverter system. This paper firstly proposes a novel distributed control strategy to achieve multiple control objectives of grid-connected combined system, which includes power balance, suppression of resonance spikes, and high power factor of grid current. Then a hot plugging scheme dedicated to ISOS grid-connected inverter system is put forward to actualize redundancy. Meanwhile, the timing sequence is introduced. Finally, the prototypes are fabricated in the lab and the experimental results are exploited to verify the effectiveness of the proposed methods.